PalpAid: Multimodal Pneumatic Tactile Sensor for Tissue Palpation

The tactile properties of tissue, such as elasticity and stiffness, often play an important role in surgical oncology when identifying tumors and pathological tissue boundaries. Though extremely valuable, robot-assisted surgery comes at the cost of reduced sensory information to the surgeon; typically, only vision is available. Sensors proposed to overcome this sensory desert are often bulky, complex, and incompatible with the surgical workflow. We present PalpAid, a multimodal pneumatic tactile sensor equipped with a microphone and pressure sensor, converting contact force into an internal pressure differential. The pressure sensor acts as an event detector, while the auditory signature captured by the microphone assists in tissue delineation. We show the design, fabrication, and assembly of sensory units with characterization tests to show robustness to use, inflation-deflation cycles, and integration with a robotic system. Finally, we show the sensor's ability to classify 3D-printed hard objects with varying infills and soft ex vivo tissues. Overall, PalpAid aims to fill the sensory gap intelligently and allow improved clinical decision-making.